TY - CONF A1 - Schwenk, C. A1 - Kannengießer, Thomas A1 - Rethmeier, Michael T1 - Restraint conditions and welding resiudal stresses in self-restrained cold cracking test N2 - In the last decade, high-strength fine grained steels and welding consumables have gained a strong raise of application ranging from mobile cranes to bridge constructions. However, the cracking susceptibility of these steels increases significantly in correspondence with the achieved improvements in yield strength and the loss in plastic deformation reserves. In order to determine this behavior a series of different standardized cold cracking tests has been developed. One remaining major problem of these tests is the uncertainty about the quantitative intensity of the restraint conditions as well as the corresponding welding residual stresses. Consequently, the comparison of different tests and welding conditions as well as the transferability of the results onto real parts is difficult at best. The main topic of this paper is the analysis of the restraint conditions and their link with the welding induced residual stresses. The importance of the given standardized selfrestrained tests and first results about the transferability of results onto real parts are discussed. The influence of the test specimen geometry on the restraint conditions of the test is investigated for a selected test with numerical Simulation using commercial FEA software. Additionally, the residual stresses caused by the welding process are measured and linked with the restraint conditions which are defined mainly by the geometry parameters. Finally the transferability of the selected cold cracking test results is validated experimentally. The test results of a multilayer weld on high-strength fine grained steel of real size weldments are investigated. For these experiments a 16 MN large scale testing facility is used which is capable of applying the high reaction forces and clamping conditions found at large scale demonstrator parts. The results show the importance of the quantitative knowledge of the restraint conditions and the welding residual stresses on the cold cracking resistance. T2 - 8th International Conference on Trends in Welding Research CY - Pine Mountain, USA DA - 01.06.2008 KW - Cold Cracking Test KW - Intensity of Restraint PY - 2008 DO - https://doi.org/10.1361/cp2008twr766 SP - 766 EP - 771 PB - ASM international AN - OPUS4-47623 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Weber, Gert A1 - Rethmeier, Michael T1 - Spot welding and weldbonding of high strength steels for lightweight auto body manufacturing N2 - The resistance spot weiding procedure is one of the most important joining technique in lightweight car body shell mass production. Especially for newly developed ultra high strength steels (UHSS) and advanced high strength steels (AHSS), this joining technique has more advantages than other thermal and mechanical joining procedures for thin Steel sheets. Additionally, the technique of adhesive bonding and its combination with the technique of resistance spot weiding called weldbonding becomes more and more important. The weldbonding affords many advantages, e.g. improved crash performance, fatigue behaviour and corrosion resistance. The main target of the contribution is to show the influence of different joined ultra and advanced high strength steels on the process reliability for both the resistance spot weiding process and the weldbonding process. In this connection the influence of surface conditions of the steel sheets, the applied adhesive and the choice of the weiding parameters on the process reliability will be studied. The results for the weldbonding procedure are based on different adhesives. Based on the representation of weiding current ranges by weldability lobes, Statements concerning the weldbonding process reliability for some special AHSS and UHSS will be given. The mechanical behaviour of spot welded and weldbonded joints for different AHSS and UHSS will be studied. T2 - EUROJOIN 8 - 8th European conference CY - Pula, Croatia DA - 24.05.2012 KW - Spot welding KW - Weldbonding KW - High strength steels KW - Process reliability KW - Mechanical properties of joints PY - 2012 SP - 633 EP - 643 AN - OPUS4-26383 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Liu, X. C. A1 - Wu, Chuan Song A1 - Rethmeier, Michael A1 - Pittner, Andreas T1 - Mechanical properties of 2024-T4 aluminium alloy joints in ultrasonic vibration enhanced friction stir welding N2 - Ultrasonic vibration enhanced friction stir welding (UVeFSW) is a recent modification of conventional friction stir welding (FSW), which transmits ultrasonic vibration directly into the localized area of the workpiece near and ahead of the rotating tool. In this study, a high strength aluminium alloy (2024-T4) was welded by this process and conventional FSW, respectively. Then tensile tests, microhardness tests and fracture surface analysis were performed successively on the welding samples. The tests results reveal that ultrasonic vibration can improve the tensile strength and the elongation of welded joints. The microhardness of the stir zone also increases. KW - Ultrasonic vibration KW - Friction stir welding KW - Mechanical properties PY - 2013 UR - https://www.researchgate.net/publication/286735810_Mechanical_properties_of_2024-T4_aluminium_alloy_joints_in_ultrasonic_vibration_enhanced_friction_stir_welding VL - 22 IS - 4 SP - 8 EP - 13 AN - OPUS4-40773 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rethmeier, Michael T1 - Laserstrahl-Hybridschweißen für Rohranwendungen N2 - Mechanische Eigenschaften der laserhybridgeschweißten Schweißverbindungen von hochfesten niedriglegierten Stählen erfüllen die Anforderungen der geltenden Normen Eindringtiefe des Zusatzwerkstoff bis ca. 12 mm Halborbitales Schweißen an 36” Rohren mit einer Wandstärke von 16 mm bei einer Schweißgeschwindigkeit von bis zu 2,2 m/min und Laserleistung von 19 kW technisch möglich Rissfreie Schweißverbindungen an Präzisionsrohren können durch eine geeignete Schweißparameterauswahl mittels Laser-Hybridverfahren hergestellt werden T2 - IW-Kolloquium CY - Hannover, Germany DA - 07.05.2014 KW - Laserstrahlquelle KW - Hybridprozesse KW - MSG-Schweißen PY - 2014 AN - OPUS4-38338 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rethmeier, Michael T1 - Experimental and numerical investigation of an electromagnetic weld pool control for laser beam welding N2 - Drop-out of molten material was avoided by EM pressure Compensation of the hydrostatic pressure of up to 20 mm thick aluminum and stainless steel (experiment and FEM) Mitigation of the weld bead dynamics Significant changes in the velocity distributions in the weld pool Weld pool geometry shape changes due to Hartmann effect Significant porosity reduction Surface quality improvements T2 - LANE 2014 -8thInternational Conference on Photonic Technologies CY - Fürth, Germany DA - 08.09.2014 KW - Welding of thick metal plates KW - AC weld pool support KW - Welding of aluminum KW - Welding of AlMg3 PY - 2014 AN - OPUS4-38349 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rethmeier, Michael T1 - Experimental and numerical investigation of an electromagnetic weld pool control for laser beam welding N2 - Drop-out of molten material was avoided by EM pressure Compensation of the hydrostatic pressure of up to 20 mm thick aluminum and stainless steel (experiment and FEM) Mitigation of the weld bead dynamics Significant changes in the velocity distributions in the weld pool Weld pool geometry shape changes due to Hartmann effect Significant porosity reduction Surface quality improvements T2 - LANE 2014 -8thInternational Conference on Photonic Technologies CY - Fürth, Germany DA - 08.09.2014 KW - Welding of thick metal plates KW - AC magnetic fields KW - AC weld pool support KW - Welding of aluminum PY - 2014 AN - OPUS4-38368 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rethmeier, Michael T1 - Influence of weld imperfections on the fatigue behaviour of resistance spot welded advanced high strength steels N2 - The influence of two different weld imperfections (gap/crack) on the fatigue behaviour of spot welded joints was tested Surface cracks havenoinfluenceon thefatiguelife Samples with cracks in the electrode indentation /HAZ where tested Stiffness curves are not significantly influenced by surface cracks 3D FE-Simulation demonstrate no changes of stress due to surface imperfections T2 - 11th International Fatigue Congress CY - Melbourne, Australia DA - 02.03.2014 KW - 3D FE-simulation KW - Cracks in the HAZ PY - 2014 AN - OPUS4-38343 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael ED - Bakir, Nasim T1 - Numerical simulation of solidification crack formation during laser beam welding of austenitic stainless steels under external load N2 - Solidification cracking phenomena taking place under Controlled Tensile Weldability (CTW) test conditions have already been investigated both experimentally and numerically via FEA in order to get a better understanding of the mechanisms of hot crack formation during laser beam welding of austenitic steel grades. This paper develops a three dimensional finite element model employing the contact elements technique to simulate the formation and propagation of solidification cracks during laser full penetration welding of fully austenitic stainless steel 1.4376. During the experimental procedure the resulting strain and displacement directed to the laser beam in the Close vicinity of the weld pool was measured at the surface of the workpiece using a Digital Image Correlation (DIC) technique with an external diode laser as an illuminating source. Local strain fields, global loads and crack lengths predicted by the model are in good Agreement with those observed in experiments. T2 - The 3rd IIW South‐East European Welding Congress CY - Timisoara, Romania DA - 03.06.2015 KW - Solidification cracking KW - DIC technique KW - Laser beam welding KW - Contact element KW - FEA PY - 2015 SN - 978-606-554-955-5 SP - 1 EP - 6 CY - Timisoara, Romania AN - OPUS4-36519 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Petrat, Torsten A1 - Graf, B. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Build-up strategies for generating components of cylindrical shape with laser metal deposition N2 - Laser Metal Deposition LMD) as additive manufacturing process offers the potential to produce near net shape components. This reduces the amount of material and post-processing. The components are composed of individual layers. Already mall irregularities within a layer can add up over multiple layers and lead to error propagation. This paper deals with the issue of build-up strategies to minimize irregularities and prevent error propagation. Different travel paths and the influence of a changing starting point regarding to error propagation are discussed. Different deposition rates between core and peripheral area are detected and successfully compensated by adjusting the build-up sequence. Stainless steel and titanium alloy Ti-6Al-4V are used in the experiments. The results are intended to illustrate the potential of an adjusted build-up strategy and provide basic information on the way to an automated deposition process. This paper is of interest for engineers in industry or science using LMD as additive manufacturing process. T2 - Lasers in Manufacturing Conference 2015 CY - Munich, Germany DA - 22.06.2015 KW - Ti - 6Al - 4V KW - Additive Manufacturing KW - Build - up Strategy KW - Laser Metal Deposition KW - Stainless Steel PY - 2015 UR - http://www.wlt.de/lim/Proceedings/Stick/sessions.html SP - 1 EP - 6 AN - OPUS4-37829 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Na, S.-J. A1 - Han, S.-W. A1 - Muhammad, S. A1 - Zhang, L. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael A1 - Karhu, M. A1 - Kujanpa, V. T1 - Flow and Bead Formation Characteristics in High Power Laser Welding at Different Welding Positions (Invited Talk) N2 - The numerical simulations of high power laser keyhole welding at different welding positions are performed by using Volume-Of-Fluid (VOF) method. The main material is SS400. The multi-physics phenomenon is considered using several models, such as the heat flux of Gaussian heat source, the recoil pressure with Clausisus-Clapeyron equation, the Marangoni flow considering temperature gradient, the buoyancy force with Boussinesq approximation, the additional shear stress and heat source due to metallic vapor ejected through keyhole entrance, the bubble formation assumed as adiabatic bubble, and the multiple-reflection by solving proper discriminant, are used. To analyze the fluid flow pattern, the concept of streamline formed by reconstructing the value of the velocity vector is applied. Partial and full penetration cases at different welding positions are considered. The welding position seems to have only a minor influence on bead formation characteristics in both cases. This is probably due to the fact that the recoil pressure has a major influence when compared to other driving forces. The flow characteristics and fluid velocity in weld pool are analyzed to compare the gravity direction effect at different welding positions. It is observed that the clockwise flow pattern is mainly formed by the recoil pressure on the keyhole surface in the case of partial penetration. The laser energy can't maintain the whole weld pool when the weld pool size becomes too large. And then the solidification starts from the middle part of weld pool and a necked weld pool shape is formed. In the full penetration welding, the weld pool flow patterns are affected by the leakage of laser power through the full penetration keyhole and also by surface tension. Furthermore, the numerical simulation of full penetration welding with AISI316L is also performed to analyze the effect of material properties. The weld bead shapes obtained by simulations were compared with the corresponding experimental results to confirm the validity of the process models adopted and the CFD simulation tool. T2 - Lasers in Manufacturing Conference 2015 CY - München, Germany DA - 22.06.2015 KW - Macro Processing (Joining, Welding) KW - Weld pool KW - Flow pattern KW - Different welding position KW - Numerical simulation KW - High power laser keyhole welding PY - 2015 SP - 1 EP - 6 AN - OPUS4-37163 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bachmann, Marcel A1 - Kunze, R. A1 - Avilov, Vjaceslav A1 - Rethmeier, Michael T1 - Finite element modelling of an AC electromagnetic weld pool support in full penetration laser beam welding of thick duplex stainless steel plates N2 - An electromagnetic weld pool support system for 20 mm thick duplex stainless steel AISI 2205 was investigated numerically and compared to experiments. In our former publications, it was shown how an AC magnetic field below the process zone directed perpendicular to the welding direction can induce vertically directed Lorentz forces. These can counteract the gravitational forces and allow for a suppression of material drop-out for austenitic stainless steels and aluminum alloys. In this investigation, we additionally adopted a steady-state complex magnetic permeability model for the consideration of the magnetic hysteresis behavior due to the ferritic characteristics of the material. The model was calibrated against the Jiles-Atherton model. The material model was also successfully tested against an experimental configuration before welding with a 30 mm diameter cylinder of austenitic stainless steel surrounded by duplex stainless steel. Thereby, the effects of the Curie temperature on the magnetic characteristics in the vicinity of the later welding zone were simulated. The welding process was modelled with a 3D turbulent steady-state model including heat transfer and fluid dynamics as well as the electromagnetic field equations. Main physical effects, the thermo-capillary (Marangoni) convection at the weld pool boundaries, the natural convection due to gravity as well as latent heat of solid–liquid phase transitions at the phase boundaries were accounted for in the model. The feedback of the electromagnetic forces on the weld pool was described in terms of the electromagneticinduced pressure. The FE software COMSOL Multiphysics 4.2 was used in this investigation. It is shown that the gravity drop-out associated with the welding of 20 mm thick duplex stainless steel plates due to the hydrostatic pressure can be prevented by the application of AC magnetic fields between around 70 mT and 90 mT. The corresponding oscillation frequencies were between 1 kHz and 10 kHz and the electromagnetic AC powers were between 1 kW and 2.3 kW. In the experiments, values of the electromagnetic AC power between 1.6 kW and 2.4 kW at oscillation frequencies between 1.2 kHz and 2.5 kHz were found to be optimal to avoid melt sagging or drop-out of melt in single pass fullpenetration laser beam welding of 15 mm and 20 mm thick AISI 2205. T2 - ICALEO 2015 - 34th International congress on applications of lasers & electro-optics CY - Atlanta, GA, USA DA - 2015-10-18 KW - Electromagnetic weld pool support KW - Laser beam welding KW - FE simulation KW - Duplex stainless steel PY - 2015 SN - 978-1-940168-05-0 SP - 650 EP - 659 AN - OPUS4-35036 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Investigation of solidification cracking susceptibility of laser welded joints of austenitic stainless steels N2 - Laser welding is a widely established manufacturing process in many industry sectors. Solidification cracking represents one of the most inadequately solved problems in welding and has major economic implications. The avoidance of hot crack forms for most fusion welding processes poses a key challenge for an important range of metallic construction materials and affects not only the manufacturers of welding equipment and material manufacturers, but also a large number of customers using welding technologies, as well as welding technical standardization and research. Solidification cracking susceptibility was examined with the help of the Controlled Tensile Weldability Test (CTW) developed by Federal Institute for Materials Research and Testing (BAM), Berlin. The test is based on the fact that hot crack formation depends on a critical strain that emerges within a critical temperature range, the so called brittle temperature range (BTR). Using this test and defined investigation programme a centreline solidification crack was generated. By controlling the applied strain during the laser beam welding process, it was possible to determine the critical strain and strain rate that led to solidification cracking formation. The hot cracking susceptibility of the tested stainless steels was qualified and quantified. The results demonstrate that the crack length increases with increasing applied strain. Furthermore, the strain rate has a significant influence on the formation of the solidification crack. T2 - 3rd International conference in Africa and Asia CY - Luxor, Egypt DA - 02.11.2015 KW - Laser beam welding KW - Hot cracking KW - Solidification cracking KW - Hot cracking test PY - 2015 SP - A-29, 1 EP - A-29, 9 AN - OPUS4-36522 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rethmeier, Michael T1 - Experimental study and numerical simulation of hot crack formation for novel laser weldability test N2 - Hot cracking susceptibility in laser beam welding was assessed for several stainless steels by means of the CTW test The strain rate has a significant influence on the formation of the hot crack It was possible to determine the critical strain and strain rate that led to shot crack formation A material ranking of hot cracking resistance could be made.A three-dimensional FEM using the contact element technique to simulate hot cracking during LBW under external load conditions was developed. Good agreement between the strain field measured using the DIC technique and the simulation results Susceptibility to hot cracking can be predicted by using FEM with the correct mechanical and thermo-physical material properties T2 - 8th International Conference Beam Technologies & Laser Application CY - St. Petersburg, Russia DA - 21.09.2015 KW - CTW-Test KW - Investigated materials KW - FEM study KW - Hot cracking PY - 2015 AN - OPUS4-38347 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rethmeier, Michael T1 - Laser-GMA-hybrid welding of longitudinally welded large-diameter pipes of grades API- X80/ X120 N2 - Potentials of the hybrid laser arc welding processes were investigated regarding reliable production of longitudinal welds of high strength pipe steels X80 and X120 Hybrid laser arc welding of the root pass: Significant reduction in the weld cross section – savings of filler material Lower heat input into the base material - improvement of mechanical properties of the weld joint  The arc type does not have any influence on the character of dilution in the laser part of the hybrid weld  14 mm deep root face was considered as optimum. No penetration of the filler material could be detected beyond this depth limit Metal powder filler wires, micro alloyed with Ni and partly with Cr and Mo, guaranteed sufficient Charpy impact toughness at low temperature for the both investigated materials: Hybrid laser arc welding is a very efficient process for the root pass in multi-pass welding and opens a large technical and economic potential for the manufacture of large pipes T2 - The METEC and 2nd European Steel Technology and Application Days (ESTAD)conference CY - Düsseldorf, Germany DA - 15.06.2015 KW - High power laser KW - Hybrid laser arc welding KW - Weld specimens KW - Charpy V-notch tests KW - Tensile tests PY - 2015 AN - OPUS4-38342 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rethmeier, Michael T1 - Development of a test method for determining the cracking susceptibility of resistance spot welded high strength steel sheets N2 - Test procedure to characterize the cracking susceptibility of RSW-steels has been developed During externally loaded test procedure all investigated steels (HDT780CD+Z100, HDT780C+ZE75/75, HX340LAD+Z100, HCT690TD+Z100) showed a cracking behavior With increased specimen load, the crack length grows for the micro-alloyed-steel and TRIP-steel Complex phase steels behavior during test procedure: Crack length growth with increasing force could not be determined The cracking susceptibility of electro-galvanized steels is less than hot-dip galvanized steels (in this case) 30 T2 - The METEC and 2nd European Steel Technology and Application Days (ESTAD)conference CY - Düsseldorf, Germany DA - 15.06.2015 KW - Externally loaded hot cracking test KW - Variables influencing hot cracking KW - Self-restraint hot cracking KW - Welding jig PY - 2015 AN - OPUS4-38348 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Investigation of hot crack susceptibility of laser welded joints of four austenitic steels N2 - Laser welding is a widely established manufacturing process in many industry sectors. Solidification cracking represents one of the most inadequately solved problems in welding and has major economic implications. The avoidance of hot crack is for most fusion welding processes a key challenge for an important range of metallic construction materials and affects not only the manufacturers of welding equipment and material manufacturers, but also a large number of customers using welding technologies, as well as welding standardization and research. In this study a new investigation programme has been developed to qualify the hot cracking susceptibility of a variety of austenitic stainless steels. The results show the possibility of using this technique to determinate the critical values that occur with initiation of solidification cracking during laser beam welding T2 - The METEC and 2nd European Steel Technology and Application Days CY - Düsseldorf, Germany DA - 15.06.2015 KW - Laser beam welding KW - Hot cracking KW - Solidification cracking KW - Hot cracking test PY - 2015 SP - 1 EP - 5 AN - OPUS4-36525 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Experimental study and numerical simulation of hot crack formation for novel laser weldability test. N2 - Laser beam welding is a widely established manufacturing process in several industries. The solidification cracking seriously effecting the safety of welded joints could arise during the beam welding of stainless steels caused by high solidification rates. In this study the controlled tensile weldability test (CTW) was used to investigate the solidification cracking susceptibility the fully austenitic stainless steels CrMnNi (1.4376), CrNi (1.4301), CrNiMo (1.4404) and CrNiSi (1.4828) during laser beam welding. The test facility allows welding of specimens with simultaneous application of tensile load along or cross to the welding direction while the speed of tensile force application is either constant or increases linearly. The tensile force increment and/or the displacement are set by means of a CNC controller. Trials were conducted by varying the ultimate tensile strain and cross-head speed while keeping the welding parameters constant. By observing the crack-no crack behaviour and estimating the generated crack length for each trail using a new optimized experimental procedure the influence of the two important conditions (the strain and the strain rate) for the formation of solidification cracks can be investigated, the critical values of strain and strain rate that are responsible for solidification cracking formation have been determined. In the present study a three-dimensional FEM using the contact element technique was developed to simulate the solidification cracking during laser full penetration welding under external load conditions for the steel 1.4376 in order to get a better understanding of the mechanisms of hot crack initiation and the theoretical results were compared to the experimental ones. By comparing the resulting solidification crack with simulated crack, it is possible to determine the critical condition of solidification crack formation in the region where the strains and the strain rates cannot be measured due to the high temperature. The results show a good agreement between numerical calculation and experiment. It is proposed that the solidification cracking susceptibility may be predicted by FEM analysis by using the correct mechanical and thermo-physical constants of the materials. T2 - BEAM TECHNOLOGIES & LASER APPLICATION CY - St. Petersburg, Russia DA - 21.09.2015 KW - Solidification cracking KW - Hot cracking test KW - FEM KW - Laser beam welding PY - 2015 SN - 978-5-7422-5150-7 SP - 55 EP - 68 AN - OPUS4-36615 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gook, S. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael ED - Schneider, G. ED - Zschech, E. ED - Petzow, G. T1 - Laserstrahl-MSG-Hybridschweißen von Rohren aus Hochfestem Stahl API-X80/ -X100 N2 - Das Laser-MSG-Hybridschweißverfahren führt bei untersuchten hochfesten Pipelinestählen API X80 und X120 reproduzierbar zu Schweißverbindungen mit anforderungsgerechten Zähigkeitseigenschaften. Eine metallurgische Beeinflussung der Schweißnahtzähigkeit ist durch eine gezielte Auswahl des Zusatzwerkstoffes möglich, wobei die maximale Eindringtiefe des Zusatzwerkstoffes in die Tiefe der Laserhybridnaht zu beachten ist. Die maximal erzielbare Eindringtiefe des Zusatzwerkstoffes ist auf ca. 14 mm begrenzt. Die eingesetzte Art des MSG-Lichtbogens hatte keinen erkennbaren Einfluss auf die Aufmischung im Laseranteil der Laserhybridnaht. Die besseren Ergebnisse der Kerbschlagzähigkeit konnten mit Metallpulverdrähten erreicht werden. Mit den erzielten gemittelten Werten der Schlagarbeit: ca. 200 J bei -60°C für X80 und ca. 53 J bei -40°C für X120 werden Anforderungen der Norm API 5L und DIN EN 10208-2 für die beiden untersuchten Grundwerkstoffe erfüllt. T2 - 49. Metallographie-Tagung CY - Dresden, Germany DA - 16.09.2015 KW - Hochfester Stahl KW - Laserstrahl-MSG-Hybridschweißen PY - 2015 SN - 978-3-88355-410-5 VL - 47 SP - 139 EP - 144 PB - Inventum CY - Sankt Augstin AN - OPUS4-44419 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Avilov, Vjaceslav A1 - Fritzsche, André A1 - Bachmann, Marcel A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Full penetration laser beam welding of thick duplex steel plates with electromagnetic weld pool support N2 - Full penetration high power bead-on-plate laser beam welding tests of up to 20 mm thick 2205 duplex steel plates were performed in PA position. A contactless inductive electromagnetic (EM) weld pool support system was used to prevent gravity drop-out of the melt. Welding experiments with 15 mm thick plates were carried out using IPG fiber laser YLR 20000 and Yb:YAG thin disk laser TruDisk 16002. The laser power needed to achieve a full penetration was found to be 10.9 and 8.56kW for welding velocity of 1.0 and 0.5 m min(-1), respectively. Reference welds without weld pool support demonstrate excessive root sag. The optimal value of the alternating current (AC) power needed to completely compensate the sagging on the root side was found to be approximate to 1.6 kW for both values of the welding velocity. The same EM weld pool support system was used in welding tests with 20 mm thick plates. The laser beam power (TRUMPF Yb:YAG thin disk laser TruDisk 16002) needed to reach a full penetration for 0.5 m min(-1) was found to be 13.9 kW. Full penetration welding without EM weld pool support is not possible-the surface tension cannot stop the gravity drop-out of the melt. The AC power needed to completely compensate the gravity was found to be 2 kW. (C) 2016 Laser Institute of America T2 - ICALEO 2015 - 34th International congress on applications of lasers & electro-optics CY - Atlanta, GA, USA DA - 2015-10-18 KW - Electromagnetic weld pool support KW - Laser beam welding KW - Duplex stainless steel PY - 2015 SN - 978-1-940168-05-0 SP - 571 EP - 579 PB - Amer inst physics CY - Melville, NY, USA AN - OPUS4-35035 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Graf, B. A1 - Gook, S. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Combined laser additive manufacturing for complex turbine blades N2 - Laser beam processes are increasingly used in the field of additive manufacturing. Prominent methods are either powderbed-based like Laser Metal Fusion (LMF), or utilizing a powder nozzle like Laser Metal Deposition (LMD). While LMF allows the manufacturing of complex structures, build rate, part volumes and material flexibility are limited. In contrast, LMD is able to operate with high deposition rates on existing parts, and materials can be changed easily during the process. However LMD shape complexity is limited. Utilizing their respective strengths, a combination of these two additive technologies has the potential to produce complex parts with high deposition rates and increased material flexibility. In this paper, combined manufacturing with additive technologies LMF and LMD is described. Its benefit for industry with emphasis on turbomachinery is shown. As reality test for the innovation, an industrial turbine blade is manufactured. KW - Turbine blade KW - Additive manufacturing KW - Laser metal fusion KW - Laser metal deposition PY - 2016 SN - 2499-9733 VL - 3 IS - 20 SP - 34 EP - 42 AN - OPUS4-38709 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rethmeier, Michael T1 - Trends in European thin sheet welding N2 - 1. Steel Production and Processing in Europe 2. Design Trends in the Automotive Industry 3. Welding Technologies in the Automotive Industry 4. Problems while Processing AHSS/UHSS 5. Challenges in Joining Multi-Material Structures 6. Mechanical Joining Technologies 7. Thermal-Mechanical Joining Processes 8. Energy Efficiency of Welding Processes T2 - AWS Sheet Metal Welding Conference XVII CY - Livonia, MI, USA DA - 19.10.2016 KW - Lightweight concepts PY - 2016 AN - OPUS4-38763 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Frei, Julian A1 - Rethmeier, Michael T1 - Influence of manufacturing conditions on the cracking susceptibility of AHSS during resistance spot welding N2 - The complex microstructure and the advanced mechanical properties of AHSS steel types lead to an increased susceptibility to weld cracking, especially during resistance spot welding under ‘rough’ manufacturing conditions. Various activities have been conducted in recent years at the Federal Institute for Materials Research and Testing (BAM) and the Fraunhofer IPK on this matter. Understandings about the safe spot weldability and the process of crack-forming itself were gained, and solutions for handling this issue given. The performed work includes investigations on the influence of initial gaps as well as restraint intensity. An experimental method for the determination of the general cracking susceptibility, i.e. a material ranking of AHSS in respective to current restraints was developed. Coupled mechanical and thermal simulations of the welding process show the present internal stress-strain-conditions and values responsible for the formation of cracks, deepening the understanding of the process. By using this easy to perform and material-independent method for the determination of the cracking susceptibility in resistance spot welded joints, small and medium sized companies can profit by rapidly evaluating the joinability of their handled material combinations as well as OEMs. T2 - Sheet Metal Welding Conference XVII CY - Livonia, Michigan, USA DA - 18.10.2016 KW - Welding under external loading KW - Cracking susceptibility of AHSS KW - Resistance spot welding KW - Initial gap PY - 2016 SP - Session 1-2, 1 EP - Session 1-2, 15 AN - OPUS4-38137 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Anwendung der digitalen Bildkorrelationstechnik zur Untersuchung der Heißrissanfälligkeit laserstrahlgeschweißter Verbindungen mit dem CTW-Test N2 - In dieser Studie wurde die Heißrissanfälligkeit beim Laserstrahlschweißen für die Werkstoffe 1.4376, 1.4301 und 1.4828 mit Hilfe des CTW­ Test quantifiziert. Bei den Versuchen konnten Erstarrungsrisse in den Proben generiert werden. Zusätzlich können mit der Bildkorrelations-Technik die lokalen Dehnungen und Dehnungs­raten während des Heißrisstests gemessen wer­ den. In Verbindung mit einem externen Dioden­laser zum Beleuchten der zu messende Oberflä­che und lnterferenzfiltern an den Kameras konn­ten die DIC Messungen ohne optische Störungen durchgeführt werden. Die Ergebnisse zeigen, dass die Heißrissbildung bei einer externen Belastung von 3 % für die Stahlsorte 1.4376 zu erwarten ist. Für die Stahls­ orte 1.4301 beträgt dieser Grenzwert 2 % und 1,5 % für die Stahlgüte 1.4828. Außerdem ist zu beobachten, dass die Gesamtrisslänge mit zu­ nehmender äußerer Zugbeanspruchung steigt T2 - 35. Assistentenseminar Füge- und Schweißtechnik CY - Institut für Werkstoff- und Fügetechnik der Otto-von­ Guericke-Universität Magdeburg DA - 01.12.2014 KW - Digitale Bildkorrelationstechnik KW - Heißrissanfälligkeit KW - Untersuchung laserstrahlgeschweißter Verbindungen KW - CTW-Test PY - 2016 SN - 978-3-945023-55-6 VL - 2016/34 SP - 50 EP - 54 PB - DVS Media GmbH CY - Düsseldorf AN - OPUS4-38065 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rethmeier, Michael T1 - European perspective on 21st century BIW joining challenges N2 - •Main Welding Technologies in the Automotive: RSW and laserbeam welding •Light Weight Design leads to increasing use of AHSS and UHSS which results in higher demands for the joining technology •Joining Multi-Material Structures offers opportunities for “new” Thermal-Mechanical Joining Processes and Hybrid Processes •In the coming years a trend towards sustainable manufacturing can be seen. Comparison between laserbeam and RSW will be a tight match! T2 - AWS Sheet Metal Welding Conference XVll CY - Livonia, MI, USA DA - 19.10.2016 KW - Resistance spot welding KW - Laser beam welding KW - Lightweight concepts KW - AHSS KW - Weld cracks PY - 2016 AN - OPUS4-38339 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rethmeier, Michael T1 - Welding with high-power lasers: trends and developments N2 - High power laser welding technology has made a large progress in the last decade and established itself in different industrial applications; Hybrid laser arc welding is one of the most prospective technologies for heavy components assembling; Modern high speed video observation, in situ x-ray screening as well as simulation techniques contributed to better understanding of laser welding process; New approaches e.g. application of electromagnetic fields for melt pool control and welding at reduced pressure ambient have significantly contributed to extending the process boundaries far beyond the known Limits. T2 - LANE 2016 CY - Fürth, Germany DA - 19.09.2016 KW - Laser hybrid welding KW - Process diagnostics and simulation KW - Electromagnetic weld support system KW - Laser beam welding under vacuum/reduced pressure PY - 2016 AN - OPUS4-38340 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rethmeier, Michael T1 - Influence of manufacturing conditions on the cracking susceptibility of AHSS during resistance spot welding N2 - The influence of two different weld imperfections (gap/crack) on the fatigue behaviour of spot welded joints was tested Surface cracks have no influence on the fatigue life Samples with cracks in the electrode indentation /HAZ where tested Stiffness curves are not significantly influenced by surface cracks 3D FE-Simulation demonstrate no changes of stress due to surface imperfections • Welding under external forces was found suitable for characterizing AHSS materials New quick and easy-to-perform procedure for establishing a material ranking regarding cracking susceptibility T2 - AWS Sheet Metal Welding Conference XVII CY - Livonia, MI, USA DA - 19.10.2016 KW - 3D-FE-Simulation PY - 2016 AN - OPUS4-38366 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Graf, B. A1 - Schuch, M. A1 - Petrat, T. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Combined laser additive manufacturing with powderbed and powder nozzle for turbine parts N2 - Metal additive manufacturing is often based on laser beam processes like Laser Metal Fusion (LMF) or Laser Metal Deposition (LMD). The LMF process is in particular suitable for very complex geometries. However build rate, part volume and material flexibility are limited in LMF. In contrast, LMD achieves higher deposition rates, less restricted part sizes and the possibility to change the material composition during the build-up process. On the other hand, due to the lower spatial precision of the material deposition process, the complexity of geometries is limited. Therefore, combined manufacturing with both LMF and LMD has the potential to utilize the respective advantages of both technologies. In this paper, combined additive manufacturing with LMF and LMD is described for Ti-6Al-4V and Inconel 718. First, lattice structures with different wall thickness and void sizes are built with LMF. The influence of LMD material deposition on these LMF-structures is examined regarding metallurgical impact and distortion. Cross-sections, x-ray computer tomography and 3D-scanning results are shown. For the titanium alloy specimen, oxygen and Nitrogen content in the deposited material are analysed to evaluate the LMD shielding gas atmosphere. The results are used to develop guidelines for a LMD build-up strategy on LMF substrates. With these findings, a gas turbine burner is manufactured as reality test for the combined approach. T2 - 6th International Conference on Additive Technologies iCAT 2016 CY - Nürnberg, Germany DA - 29.11.2016 KW - Ti-6Al-4V KW - Inconel 718 KW - Combined laser manufacturing PY - 2016 SN - 978-691-285-537-6 SP - 317 EP - 323 AN - OPUS4-38702 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Neubert, S. A1 - Pittner, Andreas A1 - Rethmeier, Michael T1 - Numerical Sensitivity Analysis of TRIP-Parameter K on Weld Residual Stresses and Weld Distortion N2 - A combined experimental numerical approach is applied for a sensitivity analysis of the transformation induced plasticity (TRIP)-parameter K on welding residual stresses and welding distortion for the welding of the low-alloyed high-strength S960QOL with the high-alloyed hig-strength filler material CN13-4-IG. A thermo-mechanical FE model of a real GMA welding process was experimentally validated against termperature field, X-Ray stress measurments and optical distortion measurement. Within the sensititvity analysis K was varied and the influence on the calculated welding residual stresses and welding distortion is evaluated by performing corresponding FEA. The correct order of K magnitude is necessary in order to reproduce the residual stresses qualitatively and quantitatively. For the sufficient reproducing of the welding distortion the transformation induced plasticity can be neglected. T2 - 11th International Seminar - Numerical Analysis of Weldability CY - Graz, Austria DA - 27.09.2015 KW - TRIP PY - 2016 SN - 978-3-85125-490-7 SN - 2410-0544 SP - 361 EP - 383 PB - Verlag der Technischen Universität Graz CY - Graz AN - OPUS4-38904 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Frei, J. A1 - Rethmeier, Michael ED - Rethmeier, Michael T1 - Einfach anwenderfreundlich - Numerische Simulation von Fügestellen N2 - Ob in der Automobilindustrie, beim Rohrleitungs- oder beim Kraftwerksbau – anspruchsvolle und hochwertige Fügeverbindungen entscheiden oft über die Qualität des Endproduktes. Um z. B. das Verzugsverhalten von Karosseriebauteilen vorab einschätzen zu können, setzen Hersteller auf die numerische Simulation der geschweißten Komponenten. Besondere Aufmerksamkeit gilt hier den Fügestellen. Da diese oft nur wenige Millimeter klein sind, kommen konventionelle Prüfverfahren wie der Zugversuch hier jedoch nicht ohne weiteres in Frage. Forscher des Fraunhofer IPK untersuchen deshalb eine alternative Methode, um die negativen Begleiterscheinungen des thermischen Schweißens im Vorfeld am PC zu analysieren und nötige Gegenmaßnahmen ableiten zu können. KW - Numerische Simulation PY - 2016 SN - 1438-1125 IS - 2 SP - 14 EP - 15 AN - OPUS4-38747 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Petrat, T. A1 - Rethmeier, Michael ED - Rethmeier, Michael T1 - Schicht für Schicht Auftragsschweißen dreidimensionaler Körper N2 - Die Anwendung der additiven Fertigung nimmt stark zu. Eine neue Designfreiheit erlaubt es hier den Konstrukteurinnen und Konstrukteuren, die Bauteilfunktion in den Vordergrund der Entwicklungen zu stellen. Leichtbaustrukturen sowie Funktionsintegration machen es möglich, vormals Bauteile aus vielen Einzelkomponenten jetzt in einem einzigen Bauteil zu vereinigen. Experten am Fraunhofer IPK qualifizieren das Laser-Pulver-Auftragschweißen für die additive Fertigung und legen dabei besonderen Wert auf die Automatisierung des Verfahrens. KW - Laser-Pulver-Auftragsschweißen PY - 2016 SN - 1438-1125 IS - 1 SP - 18 EP - 19 AN - OPUS4-38746 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rethmeier, Michael A1 - Momeni, Kaveh A1 - Schippereit, Christian A1 - Weber, Gert T1 - Einfluss von fertigungsbedingten Spalten auf das Tragverhalten der Widerstandspunktschweißverbindungen aus hochfesten Stählen N2 - In einem Forschungsvorhaben wurde der Einfluss von fertigungsbedingten Spalten von bis zu 3 mm auf das Tragverhalten der Widerstandspunktschweißverbindungen aus Stählen am Beispiel von HX340LAD+Z (Werkstoffnummer 1.0933), HCT780X+Z (1.0943), HCT980C (1.0955) und 22MnB5+AS140 untersucht. Neben spaltabhängigen Schweißbereichen wurden auch statische Festigkeit, dynamische Festigkeit sowie Schwingfestigkeit betrachtet. Schließlich wurden ein Prozesssicherheitskoeffizient sowie eine Prozess-Festigkeits-Kenngröße abgeleitet, mit deren Hilfe der Anwender das Verhalten der Punktschweißverbindungen unter Spalteinfluss beurteilen kann. KW - resistance spot welding KW - strength KW - quality assurance KW - Qualitätssicherung KW - Festigkeit KW - Widerstandspunktschweißen PY - 2016 SN - 0036-7184 VL - 68 IS - 1-2 SP - 22 EP - 27 PB - DVS Media GmbH CY - Düsseldorf AN - OPUS4-35366 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Neubert, S. A1 - Pittner, Andreas A1 - Rethmeier, Michael T1 - Experimentelle Bestimmung der umwandlungsplastischen Konstante K und deren Einfluss auf Schweißeigenspannungen N2 - Die in dieser Studie vorgestellte einfache Probengeometrie zeigt sich in Verbindung mit der angewandten Versuchs- und Auswertemethodik geeignet, um den umwandlungsplastischen (TRIP)-Parameter K unter Verwendung des thermomechanischen Simulators Gleeble® 3500 experimentell zu bestimmen. Der TRIP-Parameter K wurde für die Grundwerkstoffe S355J2+N und S960QL, sowie für den hochlegierten Zusatzwerkstoff CN13-4 -IG bestimmt. Die numerische Einflussanalyse zeigt, dass bei der Berechnung von (Oberflächen-)Schweiß­eigen-spannungen die Vernachlässigung des TRIP-Effektes kaum einen Einfluss auf die Längseigenspannungen hat. Im Gegensatz da­ zu resultieren gegenüber dem Referenzfall sig­nifikante Abweichungen der Quereigenspannungen im und um den Schweißnahtbereich. Die Verdopplung des TRIP-Parameters K ge­genüber dem Referenzfall hat nur einen ver­nachlässigbaren Einfluss auf die Längs- sowie Quereigenspannungen auf der Oberfläche. Für eine qualitative und quantitative numerische Nachbildung der experimentell bestimmten Längs- und Quereigenspannungen ist die Be­rücksichtigung der Größenordnung des materi­al-abhängigen TRIP-Parameters K notwendig. T2 - 35. Assistentenseminar Füge- und Schweißtechnik CY - Institut für Werkstoff- und Fügetechnik der Otto-von­ Guericke-Universität Magdeburg DA - 01.12.2014 KW - Umwandlungsplastischen Konstante K KW - Einfluss auf Schweißeigenspannungen PY - 2016 SN - 978-3-945023-55-6 VL - 2016/314 SP - 15 EP - 21 PB - DVS Media Düsseldorf CY - Düsseldorf AN - OPUS4-38057 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schneider, André A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Impiego di un dispositivo per il vuoto locale di tipo mobile nell'applicazione del processo laser. T1 - Deployment of mobile vacuum device in the application of laser beam welding N2 - Lo sviluppo del pennacchio di vapore durante la saldatura laser di metalli con direzioni di propagazione lungo l'asse del fascio laser comporta una riduzione della potenza del laser assorbita nel keyhole. Questi effetti negativi possono essere notevolmente attenuati mediante l'applicazione di una ridotta pressione ambientale, diminuendo così l'interazione tra il fascio laser ed i prodotti dell'evaporazione, condizione che favorisce la stabilità del processo di saldatura e si traduce in una maggiore profondità di penetrazione. Una tecnica convenzionale utilizza il principio della camera a vuoto, simile a quello utilizzato per la saldatura a fascio elettronico. L'applicazione di questa tecnica è limitata dalle dimensioni della camera e riduce quindi i vantaggi di questo approccio, particolarmente per componenti di grandi dimensioni. Abbiamo dimostrato la possibilità di applicazione del vuoto in forma localizzata con apparecchiature mobili, che consentono di generare una pressione ridotta solo in una piccola zona attorno al keyhole. Utilizzando un dispositivo di chiusura appositamente progettato per la pressione, di tipo mobile, che può essere spostato lungo l'asse del giunto è possibile ottenere una pressione assoluta di circa 200 mbar. Questo è sufficiente per aumentare la profondità di penetrazione di circa il 50%. I campioni di acciaio grado S355 sono stati saldati con una potenza laser incrementale da 5 kW a 12 kW a pressione atmosferica e confrontati con quelli saldati a pressione ambiente di 200 mbar. La valutazione della sezione longitudinale ha rivelato un aumento della profondità di penetrazione dei giunti di circa il 35%. Inoltre, sono stati eseguiti test di saldatura in configurazione di giunti testa a testa con lamiere di 15 mm di spessore con diverse potenze associate al fascio laser eseguiti a pressione atmosferica ed a pressione ambiente ridotta di circa 200 mbar. L'aumento nella profondità di penetrazione fino al 40% è relativo alla pressione ridotta. In particolare, basse velocità di saldatura con pressione ridotta si sono rivelate particolarmente vantaggiose in termini di aumento della penetrazione. N2 - The development of the vapour plume during the laser beam welding of metals with propagation directions along the laser beam axis leads to a reduction of the absorbed laser power in the keyhole. These unfavourable effects can be significantly mitigated by the application of a reduced ambient pressure thus decreasing the interaction between the laser beam and evaporation products, which leads to more stable welding process and results in increased penetration depth. A conventional technique use a vacuum chamber principle, similar to that, used for electron beam welding. Application of this technique is restricted by the chamber size and reduces thus the advantages of this approach especially for large components. We demonstrate a possibility of mobile local vacuum application, which allows to generate a reduced pressure only in small region around the keyhole. By using of specially designed mobile pressure lock which can be moved along the welding direction absolute pressure of around 200 mbar could be obtained. This is sufficient to increase the welding depth by around 50%. Samples from S355 were welded with an incremental laser power from 5 kW to 12 kW at atmospheric pressure and compared to those welded at ambient pressure of 200 mbar. The evaluation of the longitudinal section revealed an increase of the welding depth by about 35%. Furthermore, the welding trials in butt joint configuration on 15 mm thick plates at various laser beam power performed for atmospheric and reduced ambient pressure of around 200 mbar. The increase in welding depth up to 40% was established for reduced pressure. Particularly, low welding speeds under reduced pressure were especially advantageous in terms of increasing the welding depth. KW - laser welding KW - Laserstrahlschweißen KW - vacuum KW - local effects KW - Vakuum KW - Lokale Effekte PY - 2016 SN - 0035-6794 VL - 04 IS - 04 SP - 1 EP - 8 AN - OPUS4-35619 LA - mul AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gook, S. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael A1 - El-Batahgy, A.M. T1 - Laser and hybrid laser-arc welding of cryogenic 9 % NI Steel N2 - Heat treated 9%Ni steel is considered the most suitable and economic material for construction of large-size liquefied natural gas (LNG) storage tanks which operate at cryogenic temperatures (-196°C). Strength above 700 MPa as well as a minimum impact value of 60 J are required to ensure reliable operation of the LNG tanks at operating temperature. Conventional arc welding processes, including shielded metal arc welding, gas metal arc welding, gas tungsten arc welding and submerged arc welding, are currently used in construction of LNG tanks. Ni based filler wire is the preferred filler metal of choice in LNG tank construction. The main problem with this choice is the lower mechanical properties, particularly tensile strength of the weld metal. To compensate, the wall thickness needs to be excessively thick to ensure the strength of the welded structures. Ni based filler material is expensive and a large quantity is needed to fill the multi-pass weld grooves. These factors significantly add to the cost in the fabrication of LNG storage tanks. For these reasons, exploration of new welding technologies is a priority. A big potential can be seen in laser based welding techniques. Laser beam welding results in much smaller fusion zone with chemical composition and mechanical properties similar to that of the base material. Laser welding is a much faster process and allows for a joint geometry which requires less filler material and fewer welding passes. The advantages of laser welding can help to overcome the problems pointed out above. Trials of autogenous laser welding, laser cold-wire welding and hybrid laser-arc welding conducted on the 9%Ni steel are presented in this paper. Chemical composition of the weld metal as well as effects of welding parameters on the weld formation, microstructure and tensile strength is discussed. Filler wire penetration depth as well as character of its distribution in the narrow laser welds was examined using EPMA - electron probe microanalysis. KW - hardness KW - cryogenic steel KW - laser welding KW - microstructure KW - tensile strength PY - 2016 UR - http://gns.mephi.ru/sites/default/files/journal/file/en.2016.1-4.pdf SN - 2499-9733 VL - 1 IS - 18 SP - 34 EP - 45 PB - Research Nuclear University MEPHl CY - Moskau, Russia AN - OPUS4-36553 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Frei, J. A1 - Suwala, H. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Bestimmung der Rissanfälligkeit von hochfesten Stählen beim Widerstandspunktschweißen N2 - Die stetig zunehmenden Anforderungen an Kraftstoffverbrauch, Schadstoffemission, sowie passive Sicherheit haben die Automobilindustrie vor Herausforderungen gestellt, die nur durch einen konsequenten Einsatz moderner hochfester Stahlwerkstoffe zu bewältigen sind. Obgleich eine generelle Eignung dieser Stähle für das Widerstandspunktschweißen (WPS) gegeben ist, kann es durch verschiedene externe Einflüsse im betrieblichen Umfeld zur Rissbildung in der Schweißverbindung kommen. Der Einfluss dieser Risse auf die mechanischen Eigenschaften ist derzeit nicht hinreichend genau erfasst, so dass häufig die Vorgabe einer rissfreien Schweißverbindung besteht. Die Kenntnis der Rissanfälligkeit der verarbeiteten Materialkombinationen sowie von ungünstigen Schweißparametern ist daher für viele Unternehmen von erheblicher wirtschaftlicher Bedeutung. Im Rahmen des FOSTA Projekts P921 „Entwicklung eines Verfahrens zur Bestimmung der Rissanfälligkeit von hochfesten Stählen beim Widerstandspunktschweißen“ wurde ein Ansatz zur Bestimmung der Rissanfälligkeit von WPS-Verbindungen hochfester Stähle entwickelt. Mittels einer hydraulischen Vorrichtung unter Zugbelastung wurden geschweißte, rissbehaftete Proben optisch ausgewertet. Das Verfahren ist geeignet, um ein Werkstoffranking bezüglich der Rissanfälligkeit beim Widerstandspunktschweißen für Werkstoffe aufzustellen. KW - Widerstandspunktschweißen KW - Werkstoffranking KW - Rissanfälligkeit KW - hochfeste Stähle KW - Liquid Metal Embrittlement KW - Lötrissigkeit PY - 2016 DO - https://doi.org/10.3139/120.110904 VL - 58 IS - 7-8 SP - 612 EP - 616 PB - Carl Hanser Verlag CY - München AN - OPUS4-37161 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Quiroz, V. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Saldabilita di lamiere in acciaio inossidabile austenico ed austeno-ferritico ad alto contenuto di manganese con processo laser N2 - Manganese alloyed stainless steels represent a cost-effective alternative to conventional CrNi- stainless steels due to strong fl uctuations of the market prices for nickel seen during the last years. In CrMnNi steels, nickel is partially replaced by lower-cost manganese and small amounts of nitrogen for stabilization of the austenitic phase. This also brings benefi ts regarding the mechanical properties, as it results in an increased material strength. Laser beam welding of such materials was investigated for direct comparison with Standard CrNi steels. Main emphasis was laid on fi nding adequate process parameters to achieve a stable welding process and obtain a good weld quality. Two different laser sources, a 4.4 kW Nd:YAG and a 5 kW CO2 laser, were used to weld 1.5 mm stainless steel sheets in continuous wave mode. A high-Mn austenitic (1.4376) and a lean duplex (1.4162) steel, as well as the standard austenitic (1.4301) and duplex (1.4362) grades were selected as test materials. Both butt and lap joint confi gurations were studied. Experiments were carried out systematically, varying the welding speed, laser power and focal point position in order to determine adequate process windows. The infl uence of the shielding gas type and fl ow rate on the process stability and the weld quality were investigated. The effects of weld edge preparation on the weld appearance and quality levels attained were also examined. The obtained welded joints were subjected to radiographic tests for detection of internal imperfections. Also a metallurgical characterization of the samples regarding the resulting phase composition or balance and hardness depending on the welding process parameters was conducted. Furthermore, tensile and potentiodynamic tests were performed to evaluate the mechanical and corrosion properties, respectively. The results provide an insight into the advantages and limitations of the laser beam welding process for joining high-manganese alloyed stainless steels. Conditions for the production of defect-free and corrosion-resistant welds having good mechanical properties could be determined. KW - Weldability KW - Austenitic stainless steels KW - Corrosion KW - CO2 lasers KW - Duplex stainless steels KW - Laser welding KW - Manganese KW - Mechanical properties KW - Shielding gases KW - YAG lasers PY - 2016 SN - 0035-6794 VL - 68 IS - 1 SP - 33 EP - 43 AN - OPUS4-38100 LA - ita AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - RPRT A1 - Rethmeier, Michael A1 - Gumenyuk, Andrey A1 - Bakir, Nasim T1 - Entwicklung eines Verfahrens zur Untersuchung der Heißrissresistenz lasergeschweißter Verbindungen N2 - In den letzten Jahrzehnten hat sich die Strahlschweißtechnik signifikant weiterentwickelt und als effizientes und wirtschaftliches Werkzeug in der Industrie etabliert. Für die Untersuchung der Heißrissresistenz verschiedener Werkstoffe existieren zahlreiche eigen- und fremdbeanspruchende Tests. Diese wurden aber speziell für andere Schweißverfahren, insbesondere das Lichtbogenschweißen, konzipiert. Daher besteht die Notwendigkeit eines geeigneten Heißrisstests, bei dem Werkstoffe realen Strahlschweißbedingungen ausgesetzt werden können. Die Entwicklung sowie die Standardisierung einer aussagekräftigen experimentellen Methode stellen einen wichtigen Schritt auf dem Weg zur Vermeidung von Heißrissen und damit für die Gewährleistung der Sicherheit von gefügten Bauteilen dar. Ziel der Forschungsarbeiten ist es, einen geeigneten Test zur effektiven Untersuchung der Heißrissanfälligkeit von lasergeschweißten Verbindungen zu konzipieren und zu entwickeln. KW - Heißrissresistenz PY - 2016 SN - 978-3-942541-94-7 SP - 1 EP - 110 PB - Verlag und Vertriebsgesellschaft mbH CY - Düsseldorf AN - OPUS4-41846 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Petrat, T. A1 - Graf, B. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael ED - Witt, G. ED - Eichmann, M. ED - Kniffka, W. T1 - Strategien zur Erreichung eines konstanten Volumenaufbaus bei der additiven Fertigung mittels Laser-Pulver-Auftragschweißen T1 - Strategies to achieve constant build-up with laser metal deposition N2 - Der Einsatz von Hochleistungswerkstoffen verlangt nach einer hohen Endformnähe der zu fertigenden Bauteile, um den Aufwand und somit die Kosten für Materialeinsatz und Nachbearbeitung möglichst gering zu halten. Der additive Einsatz in Form des Laser-Pulver-Auftragschweißens bietet hierfür durch den gezielten Materialauftrag ein hohes Potential. Herausforderungen bestehen in Bereichen der Vorhersagbarkeit und der Reproduzierbarkeit des Materialauftrages, sowie der Fertigungszeit. Unterschiedliche Einflüsse bei der Schichterzeugung führen dabei zu Abweichungen von der Soll-Geometrie. Die vorliegenden Untersuchungen behandeln den Einfluss von Spurgeometrie, Spurüberlappung, Verfahrweg und Aufbaureihenfolge auf die entstehende Bauteilform. Die Teilung einer Lage in Rand- und Kernbereich ermöglicht einen konturangepassten Verfahrweg und eine Erhöhung der Endformnähe innerhalb einer Ebene. Die Verwendung unterschiedlicher Spurgrößen bei der Bauteilerzeugung verdeutlicht die Möglichkeiten einer hohen Auftragsrate bei gleichzeitig hoher Formgenauigkeit. Bereits kleine Unterschiede beim Materialauftrag zwischen Kern- und Randbereichen, Start- und Endpunkten sowie in Bereichen des Richtungswechsels führen aufgrund von Fehlerfortpflanzung nachmehreren Lagen zu Abweichungen in der Aufbaurichtung. Kompensierungen mittels angepasster Baustrategien werden aufgezeigt und diskutiert. Die Nickelbasislegierung Inconel 718, die Titanlegierung Ti-6Al-4V sowie der austenitische Stahl 316L sind Bestandteil der vorliegenden Untersuchungen. Die gewonnenen Erkenntnisse verdeutlichen das Potenzial einer angepassten Aufbaustrategie zur reproduzierbaren Erzeugung von Bauteilen am Beispiel unterschiedlicher Körpergeometrien. T2 - Rapid.Tech International Trade Show & Conference for Additive Manufacturing CY - Erfurt, Germany DA - 14.06.2016 KW - Laser-Pulver-Auftragschweißen KW - Additive Fertigung KW - Aufbaustrategie KW - 3DDruck KW - Ti-6Al-4V KW - Inconel 718 KW - 316L PY - 2016 SN - 978-3-446-45017-2 SP - 49 EP - 60 PB - Carl Hanser Verlag CY - München, Germany AN - OPUS4-36571 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Graf, B. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - 3D laser metal deposition in an additive manufacturing process chain N2 - Laser metal deposition is described with its applications for additive manufacturing. The necessary process chain is discussed, with regard to weld bead dimensions and 3D build-up strategy. Metallurgical cross sections, x-ray and tensile tests are conducted. As demonstrative components, a gas turbine burner and a turbine blade are shown. T2 - 1st International Congress on Welding, Additive Manufacturing and Associated Non- CY - Metz, France DA - 17.05.2017 KW - Laser metal deposition KW - Additive manufacturing KW - Ti-6Al-4V KW - Turbine industry KW - Process chain PY - 2017 UR - https://icwam.com/sites/default/files/Abstract%20book.pdf SP - AM 34-2 EP - 3 AN - OPUS4-43190 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Fritzsche, André A1 - Bachmann, Marcel A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael A1 - Hilgenberg, Kai T1 - Einsatz einer elektromagnetischen Schmelzbadstütze beim Laserstrahl-(Hybrid)schweißen dickwandiger Stahlbauteile N2 - Die experimentellen Untersuchungen innerhalb dieses Berichtes zeigen die erfolgreiche Anwendung einer elektromagnetischen Schmelzbadstütze beim Laser-strahl(hybrid)schweißen von ferromagnetischen Stäh-len mit einer Werkstückdicke von bis zu 20 mm. Bis-lang wurde dieses System zur Kompensation des hydrostatischen Druckes von Aluminiumlegierungen und austenitischen Stählen eingesetzt. Zunächst wur-den die Versuche an Duplexstählen vorgenommen, die jeweils zur Hälfte aus Austenit und Ferrit bestehen. Im Anschluss daran wurden die Versuche auf bis zu 20 mm dicke Werkstücke aus Baustahl erweitert. In-nerhalb der Versuchsreihen wurden die AC-Leistung sowie die Oszillationsfrequenz variiert. Für Werk-stückdicken von 15 mm war eine AC-Leistung von ca. 1 kW notwendig, um die Wurzelüberhöhung in die Bewertungsgruppe B der für laserstrahlgeschweißten Stähle gültigen DIN EN ISO 13919-1:1996-09 einord-nen zu können. Mit zunehmender AC-Leistung wird die Wurzelüberhöhung sukzessive reduziert. Nach erfolg-reicher Erweiterung auf ferromagnetische Werkstoffe wurde die Anwendung der Technologie für das Laser-strahlhybridschweißen demonstriert, indem praxisrele-vante Y-Nähte an 20 mm dicken Baustählen ohne Wurzelüberhöhung einlagig in Wannenlage geschweißt wurden. Trotz der Beeinflussung des Lichtbogens durch das oszillierende Magnetfeld sowie des zusätz-lich zum hydrostatischen Druck zu berücksichtigenden Lichtbogendruckes wurde eine ideale Kompensation auf der Wurzelseite erzielt. Die Erweiterung des Anwendungsspektrums der elekt-romagnetischen Schmelzbadstütze auf ferromagneti-sche Werkstoffe sowie auf das Laserstrahlhybrid-schweißen eröffnet für zukünftige industrielle Anwen-dungen ein großes Potenzial. Das einlagige Schwei-ßen dickwandiger Bauteile mittels Hochleistungslasern wird in Kombination mit der elektromagnetischen Schmelzbadstütze attraktiver. In nachfolgenden Un-tersuchungen wird der Einsatz der elektromagneti-schen Schmelzbadstütze beim Laserstrahlhybrid-schweißen von Pipelinestählen angestrebt, v. a. im Hinblick auf die Spaltüberbrückbarkeit und der me-chanisch-technologischen Eigenschaften der Schweißverbindungen. Zudem ist beim Schweißen von Duplexstählen der Einsatz von Zusatzwerkstoffen zu berücksichtigen, um das Gleichgewicht zwischen austenitischer und ferritischer Phasen zu stabilisieren. T2 - DVS Congress 2017 CY - Düsseldorf, Germany DA - 26.09.2017 KW - Elektromagnetische Schmelzbadunterstützung KW - Ferromagnetischer Stahl KW - Laserstrahl-(Hybrid)schweißen PY - 2017 SN - 978-3-96144-008-5 VL - 337 SP - 331 EP - 336 PB - DVS Media GmbH CY - Düsseldorf AN - OPUS4-42312 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Petrat, T. A1 - Marko, A. A1 - Graf, B. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael ED - Mayr, P. ED - Berger, M. T1 - Baustrategien zur Beeinflussung von Materialauftrag und Temperaturentwicklung bei der additiven Fertigung mittels Laser-Pulver-Auftragschweißen N2 - Die Weiterentwicklung des Laser-Pulver-Auftragschweißens im Bereich der additiven Fertigung stellt dieses Verfahren vor neue Herausforderungen. Bauteile können schnell und endformnah hergestellt werden, was diese Technik für den Prototypenbau sowie Kleinserienfertigung interessant macht. Die Vielzahl an Varianten, um ein Volumen aus einzelnen Schichten aufzubauen, erhöhen die Möglichkeiten die Eigenschaften des entstehenden Bauteils zu beeinflussen. Hierfür müssen Strategien entwickelt werden, welche einen gleiclunäßigen Materialauftrag bei gleichzeitig optimalen Materialeigenschaften gewährleisten. Die durchgeführten Untersuchungen behandeln den Einfluss von Pendelstrategien sowie Spiralstrategien auf die Temperaturentwicklung und stellen diese vergleichend gegenüber. Um den unterschiedlichen Bedingungen bei der Bauteilfertigung Rechnung zu tragen, wurden Versuche in Randbereichen sowie im zentralen Bereich des Testobjekts untersucht. Die Ergebnisse verdeutlichen die Notwendigkeit angepasste Baustrategien zu entwickeln, um durch einen stabilen Fertigungsprozess Qualität und Eigenschaften eines Bauteils gewährleisten zu können. T2 - FüMoTec 2017 CY - Chemnitz, Germany DA - 14.11.2017 KW - Laser-Pulver-Auftragschweißen KW - Additiv KW - Pendelstrategie KW - Spiralstrategie KW - Temperaturentwicklung PY - 2017 SN - 978-3-96100-034-0 SN - 2365-8096 SN - 2365-810X VL - 2017/2 SP - 27 EP - 36 PB - readbox unipress CY - Münster AN - OPUS4-43104 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Winterkorn, R. A1 - Petrat, T. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Temperature generation of different travel path strategies to build layers using laser metal deposition N2 - Laser Metal Deposition offers the chance to build near net shape parts. The temperature evolution within the process has an influence on track and layer geometries. There are special travel path strategies required to produce near net shape components and reduce shape deviation resulting of error propagation. This paper deals with the temperature progression of individual layers and the maximum heating of deeper substrate regions. Spiral and zig-zag strategies are examined. The investigations are carried out using S235JR as substrate and 316L as powder material. The influence of different strategies on temperature evolution is discussed. The results from the experiments show that various production strategies are associated with different temperature fields. Furthermore, the extent of the temperature variations of layer strategies and layer position are strongly dependent on the production direction. These results demonstrate the importance of developing suitable build-up strategies for parts of complex shape to ensure a stable process with constant temperature as well as even layers. T2 - Lasers in Manufacturing Conference 2017 CY - Munich, Germany DA - 26.06.2017 KW - 316L KW - Additive Manufacturing KW - Temperature behavior KW - Laser Metal Deposition KW - Stainless Steel KW - Edge effects PY - 2017 SP - 1 EP - 5 AN - OPUS4-42878 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Marko, A. A1 - Graf, B. A1 - Rethmeier, Michael T1 - Statistical analysis of weld bead geometry in Ti6Al4V laser cladding N2 - The process of laser cladding has become more important during recent years because of its broad application for cladding, repair or additive manufacturing. In the field of mechanical engineering, one use is the repair of turbine blades. For high quality and reliability of the repaired components, it is necessary to adjust the weld bead geometry to the specific repair task. The bead geometry influences the metallurgical bonding and the degree of dilution as well as the formation of defects like pores or cracks. Therefore, it is important to know the effects of the different parameters on the welding bead. A valuable tool to meet this industrial challenge is the design of experiments (DoE). In this context, the user can choose between a huge number of test plans. Greater Profit of information is expected by a larger test range. In order to confirm the acceptance, a five-step full factorial test plan is compared to a central composite design in this paper. Moreover, the limits of the experimental range are indicated and restrictions can be derived. As the results show, the essential effects are detected with a full factorial test plan as well as with a central composite design. Merely the effect strength could not always be specified unambiguously. On this account and in consideration of cost efficiency, the use of central compound design is recommended in industrial applications. KW - Laser metal deposition KW - Design of experiments KW - Laser cladding KW - Cladding parameter KW - Additive manufacturing PY - 2017 DO - https://doi.org/10.3139/120.111077 SN - 0025-5300 SN - 2195-8572 VL - 59 IS - 10 SP - 837 EP - 843 PB - Carl Hanser Verlag CY - München AN - OPUS4-42882 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hilgenberg, Kai A1 - Rethmeier, Michael A1 - Steinhoff, K. T1 - Surface structuring by pulsed laser implantation N2 - Micrometric surface topologies are required for a wide range of technical applications. While lowered surface features have been used for many years to improve the tribological behavior of contacting surfaces, there are also other fields of application, where the potential of elevated surface features is known, e. g. for metal forming tools. However, the demand for a high wear resistance of these structures often inhibits an industrial application. A solution is offered by structuring techniques that use additional material. A promising approach is the localized dispersing of hard ceramic particles by pulsed laser radiation, the so-called laser implantation. This paper describes the potential to adjust the geometry as well as the mechanical properties of laser implanted surfaces by means of microstructural and topological investigations. Afterwards, results of a wear test are given and different applications for this structuring technique are discussed. It can be shown that dome-shaped or ring-shaped structures on a micrometric scale can be produced with high hardness and wear resistance. T2 - THERMEC 2016: 9th International Conference on Processing & Manufacturing of Advanced Materials CY - Graz, Austria DA - 29.05.2016 KW - Surface structuring KW - Metal forming tools KW - Laser implantation KW - Laser dispersing PY - 2017 DO - https://doi.org/10.4028/www.scientific.net/MSF.879.750 SN - 1662-9752 VL - 879 SP - 750 EP - 755 PB - Trans Tech Publications CY - Schweiz AN - OPUS4-38927 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Meschut, G. A1 - Janzen, V. A1 - Rethmeier, Michael A1 - Gumenyuk, Andrey A1 - Frei, J. T1 - Charakterisierung des Bruch- und Festigkeits verhaltens von widerstandspunktgeschweißten Aluminiumverbindungen N2 - Die Reduktion des Fahrzeuggewichts ist ein wesentlicher Ansatz zur Ver-ringerung des Energie- und Ressourcenverbrauchs und damit zur Senkung der CO2-Emissionen im Automobilbau. In der Karosserieentwicklung kann der vermehrte Einsatz von Aluminiumwerkstoffen einen bedeutenden Beitrag dazu leisten. Im preissensitiven Umfeld des Karosseriebaus etabliert sich das bei Stahlanwendungen genutzte Widerstandspunktschweißen zunehmend auch für Aluminiumverbindungen. Verfahrensbedingte Herausforderungen, wie verkürzte Elektrodenstandzeiten und mangelnde Kenntnis über den Einfluss von Imperfektionen auf die Festigkeit, begrenzen dennoch die Weiterverbreitung des Verfahrens und stellen die Prozessrobustheit insgesamt in Frage. Im Rahmen des hier vorgestellten Forschungsvorhabens wurden das Auftreten verschiedener Brucharten experimentell untersucht und Prognosefunktionen zur Abschätzung der Tragfähigkeit von Widerstandspunktschweißverbindungen unter verschiedenen Belastungsfällen erstellt. Anschließend wurde der Einfluss von Oberflächenrissen und Rissen in der Schweißlinse auf die Scherzugfestigkeit sowohl experimentell als auch simulativ analysiert. KW - Aluminium KW - Widerstandspressschweißen KW - Rissbildung KW - Festigkeit KW - Werkstofffragen PY - 2017 UR - http://www.schweissenundschneiden.de/article/charakterisierung-des-bruch-und-festigkeitsverhaltens-von-widerstandspunktgeschweissten-aluminiumverbindungen/ VL - 69 IS - 3 SP - 126 EP - 133 PB - DVS Media GmbH AN - OPUS4-39577 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael A1 - Bakir, Nasim T1 - Comparative study of hot cracking susceptibility for laser welded joints by means of a self- restraint and an externally loaded hot cracking tests N2 - Over the past decade, laser beam welding has significantly evolved and established itself as an efficient tool in the industry. Solidification cracking and the weldability of materials have been highly contentious issues for many years. Today, there are many self and externally loaded tests to investigate the hot cracking resistance of steels. The purpose of this paper is to compare the susceptibility of three stainless steel grades to hot cracking by using an externally loaded hot cracking test (CTW) and a self-restraint test in accordance with SEP-220-3. The repeatability and effectiveness of the results are discussed. The experimental results are widely dispersed, implying a low predictive value for the self-restraint test. On the other hand, the results from the externally loaded test exhibit excellent repeatability and provide a quantitative characterization of the susceptibility of steels to hot cracking. T2 - The 5th International Conference on Steels in Cars and Trucks CY - Amsterdam-Schiphol, Netherlands DA - 19.06.2017 KW - Externally loaded test KW - Hot cracking test KW - SEP-1220-3 KW - CTW test KW - Self-restraint test PY - 2017 SP - 1 EP - 8 AN - OPUS4-41174 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Fritzsche, André A1 - Hilgenberg, Kai A1 - Teichmann, F. A1 - Pries, H. A1 - Rethmeier, Michael T1 - Electromagnetic porosity Reduction in Laser Beam Welding of Die-Cast Aluminum Alloy N2 - The present paper investigates the electromagnetic porosity reduction in partial penetration laser beam welding of 6 mm aluminum die casting AlSi9MnMg. Applying an electromagnetic field, a significant reduction of the porosity as well as smoothing of the surface of aluminum die casting can be observed. Starting from the reference case without an electromagnetic support, the porosity was reduced by 76 %. Especially big pores can be removed from the weld pool effectively due to their beneficial volume-to-area ratio whereas very small metallurgical pores tend to remain within the weld pool even when higher magnetic flux densities are applied. T2 - Lasers in Manufacturing Conference 2017 CY - Munich, Germany DA - 26.06.2017 KW - Laser beam welding KW - Die-cast aluminum KW - Porosity reduction KW - Electromagnetic influence PY - 2017 SP - 1 EP - 10 AN - OPUS4-41244 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Artinov, Antoni A1 - Bachmann, Marcel A1 - Rethmeier, Michael T1 - Transient Process Simulation of Heat Transfer in Laser Beam Welding with an Equivalent Heat Source N2 - This paper presents a multiphysics modelling framework developed for the prediction of the three-dimensional transient temperature field of the laser welding process. The numerical model consists of two studies. In the first study, a steady-state CFD process simulation of full-penetration keyhole laser beam welding was performed. Considering the effects of, thermo-capillary and natural convection, latent heat of fusion and temperature-dependent material properties up to evaporation temperature the local weld pool geometry and temperature field were obtained. These results were used in the second subsequent study as an equivalent volumetric heat source by the prediction of the transient thermal cycle during and after fusion welding. Here the energy input and the movement of the heat source were realized by a novel technique, making use of pointwise constraints and a moving mesh provided with helper lines and additional remeshing condition. The numerically calculated results were compared to experimentally observed weld pool shapes and time-temperature curves showing a very good agreement. T2 - COMSOL Conference 2017 CY - Rotterdam, Netherlands DA - 18.10.2017 KW - High power laser beam welding KW - Transient heat transfer KW - Equivalent volumetric heat source KW - Moving mesh KW - Pointwise constraints PY - 2017 SP - 1 EP - 7 CY - Rotterdam AN - OPUS4-42701 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hilgenberg, Kai A1 - Rethmeier, Michael A1 - Steinhoff, K. T1 - Surface structuring by pulsed laser implantation N2 - Micrometric surface topologies are required for a wide range of technical applications. While lowered surface features have been used for many years to improve the tribological behavior of contacting surfaces, there are also other fields of application, where the potential of elevated surface features is known, e. g. for metal forming tools. However, the demand for a high wear resistance of these structures often inhibits an industrial application. A solution is offered by structuring techniques that use additional material. A promising approach is the localized dispersing of hard ceramic particles by pulsed laser radiation, the so-called laser implantation. This paper describes the potential to adjust the geometry as well as the mechanical properties of laser implanted surfaces by means of microstructural and topological investigations. Afterwards, results of a wear test are given and different applications for this structuring technique are discussed. It can be shown that dome-shaped or ring-shaped structures on a micrometric scale can be produced with high hardness and wear resistance. KW - Laser implantation KW - Surface structuring PY - 2017 DO - https://doi.org/10.4028/www.scientific.net/MSF.879.750 SN - 0255-5476 SN - 1662-9752 VL - 879 SP - 750 EP - 755 PB - Trans Tech Publications AN - OPUS4-38263 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - RPRT A1 - Rethmeier, Michael A1 - Suwala, H. A1 - Frei, J. T1 - Entwicklung eines Verfahrens zur Bestimmung der Rissanfälligkeit von hochfesten Stählen beim Widerstandspunktschweißen N2 - Die stetig zunehmenden Anforderungen hinsichtlich geringeren Kraftstoffverbrauchs, verminderter Schadstoffemission sowie der Erhöhung der passiven Sicherheit haben die Automobilindustrie vor Herausforderungen gestellt, denen nur durch einen konsequenten Einsatz moderner Stahlwerkstoffe zu begegnen ist. Die komplexe Gefügestruktur sowie die besonderen mechanischen Eigenschaften dieser Werkstoffe verursachen jedoch eine erhöhte Neigung zur Ausbildung von Rissen insbesondere bei Widerstandspunktschweißverbindungen.Insbesondere für kleine und mittelständische Unternehmen, die keine zeitaufwendigen und teuren Voruntersuchungen bezüglich der Rissanfälligkeit von Stählen während des Widerstandspunktschweißens durchführen können, ist zum Erhalt der Wettbewerbsfähigkeit die Kenntnis der Rissanfälligkeit einer von ihnen zu verarbeitenden Materialkombination von erheblicher Bedeutung. Durch eine einfach durchzuführende, werkstoffunabhängige Methode zur Bestimmung der Rissanfälligkeit beim Widerstandspunktschweißen, kann den KMUs die Möglichkeit zur schnellen und kostengünstigen Bewertung der Verarbeitungssicherheit zu verarbeitender Materialverbindungen bereitgestellt werden. Ziel des Forschungsvorhabens ist daher die Entwicklung einer einfachen und fertigungsnahen Methode zur Bestimmung der Rissanfälligkeit hochfester Stähle während des Widerstandspunkschweißens, die auf der gezielten, reproduzierbaren Erzeugung von Rissen basiert. Es wurde eine solche Prüfmethodik entwickelt, die auf einfach durchzuführenden experimentellen Versuchen basiert. Zu untersuchende Proben werden während des Schweißvorgangs mit einer Zugkraft belastet. Hierfür wird eine hydraulische Vorrichtung genutzt, die taillierte Flachzugproben mit definierter Kraft beaufschlagt. Infolge dessen stellt sich ein Spannungszustand ein, der die Rissbildung begünstigt. Somit können ausreichende Rissentstehungsraten erzielt werden, die eine vergleichende Beurteilung der resultierenden Risslängen zwischen den Werkstoffen zulassen. Die einfache, mobile Zugvorrichtung ermöglicht eine Nutzung der bestehenden Anlagentechnik. Durch eine Normierung der resultierenden Risslängen auf die Streckgrenze des Werkstoffs und die belastete Querschnittsfläche lassen sich ein Werkstoffranking beziehungsweise eine Klassifizierung der Rissanfälligkeit der untersuchten hochfesten Materialkombinationen erstellen. Auch zukünftig entwickelte Stahlwerkstoffe potentiell höherer Festigkeiten können untersucht werden. Weiterhin kann die entwickelte Methode als Grundlage für die Gewinnung von Basisdaten zur Untersuchung verschiedener Rissentstehungsarten während des Widerstandspunktschweißens eingesetzt werden. KW - Rissanfälligkeit PY - 2017 SN - 978-3-946885-09-2 VL - 921 SP - 1 EP - 78 PB - Verlag und Vertriebsgesellschaft mbH CY - Düsseldorf AN - OPUS4-39651 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -